The present invention relates to a copy image adjustment method for use in an electrophotographic copying machine.
Methods are known for adjusting copy image. In one of them used on an electrophotographic copying machine without an exposure detection apparatus and an apparatus for detecting the surface potential of a photoconductor (hereinafer referred to as a photoconductor surface potential detector), a service man checks the copying condition of an original and adjusts the image quality by changing some of the conditions of the copying process by a method of trial and error by use of his own judgment or performs a similar adjustment by reference to a trouble shooting manual.
In another method, used on an electrophotographic copying machine without the exposure detection apparatus and the photoconductor surface potential detector, the copying process conditions, such as charging current, exposure lamp voltage, and development bias voltage are reset at their respective initial values by use of a check meter and a copy is made by use of a test chart and the thus-copied image is compared with a reference image density sample. By referring to the results of such comparison, a toner concentration setting value is changed, so that the process conditions are corrected.
In still another method, used on an electrophotographic copying machine with the photoconductor surface potential detector, the development bias voltage is checked by the surface potential detector (Japanese laid-open patent application Sho-51-98035).
According to yet another method, a standard original is copied, and charging, exposure and smearing of the optical system are detected and corrected.
Since, in the first-mentioned method, the copying condition is corrected intuitively without measuring any characteristics of the copying process, the copying process cannot always be adjusted to the same condition as the initial condition, although the copy image can be adjusted apparently satisfactorily to some extent. This makes the copying process unstable and shortens the service maintenance cycle.
In the second method those characteristic values that can be measured easily in general can be well measured practically, but those that cannot be measured easily in general, such as toner concentration, fatigue of developer, brightness of an exposure light source, smearing of an optical system, a charging apparatus and a photoconductor, cannot be measured practically. The adjustment by this method is still insufficient.
For example, when the toner concentration is measured and found to require that its setting value be changed, the toner concentration is so slow in response to such change that the setting value has to be changed gradually while checking 30 copies or so. This takes a lot of time.
In the third method, the development bias voltage is measured by use of the photoconductor surface potential detector, but the development bias voltage can be easily measured by a tester. Thus, the use of the photoconductor surface potential detector is not always advantageous. Furthermore, in this method, only the development bias potential can be checked.
In the fourth method, the conditions of the copying process can be detected and corrected up to the step of a latent electrostatic image formation. However, the conditions of the succeeding processes, particularly, toner concentration and fatigue of developer in the development process, cannot be measured. Accordingly, the toner concentration and development bias voltage cannot be adjusted appropriately, and timing for exchanging the developer cannot be determined by this method.